At the present time, in order to provide environmental test conditions, full scale test samples are placed in a walk-in size environmental chamber. The chamber is then heated, usually by convection, to an upper air test temperature, typically 180.degree. F., and then held for sample equilibration, typically one-half hour. The chamber is then cooled to a lower test temperature, typically -- 20.degree. F. and the chamber air temperature is then again held for typically an hour, to allow sample temperature equilibration. The temperature cycle is then repeated until failure of the test samples is noted by visual inspection. Cycle time is nominally eight hours.
Attempts to speed up this cycle time have been made in the past, as shown in U.S. Pat. No. 2,807,216, Lindwedel, et al., which uses a rotating cylinder containing cavities to hold samples therein and which may be rotated between two test chambers held at different temperatures. Also, U.S. Pat. No. 4,729,246, Melgaard, et al., discloses a plurality of test chambers with products to be tested mounted on a product carrier which in turn is moved by a product carrier transfer assembly.
All of the thermal cycle test systems of the prior art appear to have the disadvantage of either long cycle time or expensive equipment to move a test sample from one temperature zone to another.